LEAVING WATER
SUCTION
\
INLET
COOLER TUBE
CONNECTION
THERMISTOR..
ENTERING
COOLER
WATER SENSOR
Fig. 4
Cooler Sensor Locations
Thermistors mis-located or out of
calibration.
Code 68 and 69, Low Suction Superheat
if the follow-
ing logic is satisfied, then all the compressors on the
circuit
be stopped.
Suction superheat is equal to 0°F
or the satu-
rated suction is greater than 58 F (14.4 C) and either
condition has been true for more than 5 minutes.
Possible causes for this failure are a stuck electronic
expansion valve or thermistors mis-located or out of
calibration.
To reset, use the manual reset method.
Code 71 to 81, Thermistor Failure
If the measured
temperature of a thermistor is less than
F (-51 C)
(363,000 ohms) or greater than 240 F (116 C) (2 16 ohms),
the appropriate sensor error code will be displayed and
the unit
be stopped. The thermistor failures will
automatically reset. The following is a summary of
possible causes.
Thermistor Failure
A shorted or open circuit ther-
mistor will cause the failure.
Wiving
Failure
A shorted or open circuit will cause
the failure.
Module
If the circuitry in the pro-
cessor module fails, the error could occur.
NOTE: The reset thermistor is an optional thermistor
and is only used with outside or space temperature reset.
It will only be read by the processor if the unit is con-
figured for outside or space temperature reset.
The absence of a thermistor failure does not necessarily
mean that a thermistor is accurate. To determine
accuracy, the reading must be compared with a measure-
ment of the actual temperature to which the thermistor
probe is exposed.
Quick Test
The Quick Test feature allows the service
technician to individually test all the inputs and outputs
of the control system.
The test function operates the Quick Test diagnostic
program. When the unit is in STANDBY mode, the test
subfunctions will energize the solenoid valves, unloaders,
electronic expansion valves and compressors. The
solenoids and unloaders will energize for 3 minutes. The
electronic expansion valve
travel to fully open in one
test and to fully closed in the next. The compressors
energize for 10 seconds. The subfunctions are explained
below. Refer to Table 6 for all the elements in the
subfunctions.
NOTE: The Quick Test energizes the alarm light and
alarm relay. They will remain energized as long as the unit
is in Quick Test.
To reach a particular test, enter its subfunction number
and then scroll to the desired test with the
key. A
test can be terminated by pressing
c
l
. Pressing
after a test has started will advance the system to the
next test, whether the current one is operating or has
timed out. Once in the next step, you may start the test
by pressing
or advance past it by pressing .
c
l
c
l
While the unit is in Quick Test, you may access another
display or function by depressing the appropriate keys;
however, the unit will remain in the Quick Test func-
tion until
is entered, or, if the keyboard is
not used for 10 minutes, the unit will automatically leave
the Quick Test function. See the following example:
14
Summary of Contents for HS070-160
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